1. Field of the Invention
This invention relates to particulate organic waste based fertilizers and methods for their preparation. More particularly, it relates to organic waste based nitrogen fertilizers, exhibiting high nitrogen availabilities, and to a new method of effectively preparing them from nitrogenous organic wastes, and urea and formaldehyde. The new method relates to the discovery of new and improved conditions for reacting organic wastes with urea and formaldehyde to produce highly available nitrogen nutrients from organic wastes which normally exhibit low nitrogen availabilities as plant foods.
2. Description of Related Art
Large amounts of organic waste materials containing nitrogen are formed in municipal, industrial, and agricultural operations. Wastes, such as poultry manures, waste water solids, sewage sludges and municipal garbage are produced as damp, composted, or dried solids. The amount of nitrogen available from these waste sources is so large and has created so much environmental and economic interest that the art contains large amounts of work carried out in attempts to use these wastes as nitrogen fertilizer sources. Some of the work has involved reaction of the waste materials with formaldehyde, urea, and ureaformaldehyde concentrates and resins, in attempts to eliminate malodors, usually present in the wastes.
In U.S. Pat. No. 3,655,395, John Karnemaat disclosed a process for treating industrial and municipal wastes, suspended or dissolved in water, by stepwise treatment with concentrated formaldehyde, nitric acid, and urea, to form ureaformaldehyde condensation products which were then dried. He extended his technology in U.S. Pat. No. 3,939,280, which taught converting poultry manure by treatment with a catalytic amount of nontoxic acid, urea, and a formaldehyde supplying substance.
In U.S. Pat. No. 3,942,970, James O'Donnell disclosed a system for producing granular, high nitrogen, odorless fertilizer from sewage filter sludge. O'Donnell added acid to bring pH of the sludge to 3-5 and reacted the sludge with methylolurea at pH 3-5, and a temperature of 30 to 80.degree. C., using vigorous agitation. In U.S. Pat. No. 4,081,366, O'Donnell dewatered the reacted ureaformaldehyde-sludge mixture by vacuum filtration, and in 4,057,392, provided an apparatus and process for treating sewage sludge filter cake to provide a slow release nitrogen. The maximum availability of his nitrogen was 55 percent.
In U.S. Pat. No. 2,977,214, McLellan produced granules of nitrogenous sewage sludge by compacting between high pressure rolls, breaking the compacted pieces, and then screening to the desired particle size.
In my U.S. Pat. No. 4,997,469, a method was provided for producing high integrity, low odor, natural based granular fertilizers by mixing aqueous formaldehyde with natural nitrogenous chick waste, with or without urea, heating until some of the chick waste nitrogen was in water soluble form, forming granules, and neutralizing to pH 6.5-8.0 by adding mineral acid, and hardening the granules by heating.
The technology was further advanced in my U.S. Pat. No. 5,240,490, which provided a continuous process for non-destructive recovery of natural nitrogenous materials as particulate agricultural nutrients from poultry waste in a fluid bed granulator. Maximum nitrogen Availability Index provided was 45.5 in those products.
Thus, the prior art has provided several effective methods for recovering natural waste nitrogenous materials as nitrogen fertilizers having reduced odors. For a nitrogen fertilizer to be an effective plant food, the nitrogen from that fertilizer must be substantially available in the soil to the roots and foliage of growing plants, preferably within a single growing season.
Agronomists through years of field and greenhouse studies have been able to correlate the effectiveness of water insoluble nitrogen release with an Availability Index whereby complete one season release of water insoluble nitrogen is indicated by an Availability Index of 100, while no release would be indicated by 0. The Availability Index is derived by equation, as follows: ##EQU1##
CWIN is determined by method 2,057 and NPIN is determined by method 2,059 of the Tenth Edition of the A.O.A.C. Official Methods of Analysis.
Slow release fertilizers made from nitrogenous wastes have been available for a long time, but until now there have been no methods provided in the prior art for increasing the normally low nitrogen availabilities in natural nitrogenous wastes to high levels so that the nitrogen from fertilizers derived therefrom is substantially available.
It is an object of this invention to provide a new method for preparing slow release nitrogen fertilizers from nitrogenous wastes which exhibit substantially complete availability of the nitrogen.
It is a further object of this invention to provide the operating parameters whereby this new method may be effectively carried out.
It is a further object of this invention to provide an improved organic waste based fertilizer exhibiting substantially complete availability of its nitrogen, prepared by the new method.